Sorry to see HTC bow out but unless you are Apple or someone else trying to sell content then this is a difficult market I guess.

http://www.coolsmartphone.com/2012/10/11/htc-drop-out-of-the-us-tablet-market

So my fag packet analysis of differentiating factors that might be necessary for Tablet success:

Google - Brand, Price,

Apple - Brand ++, Quality

Amazon - Brand, Content ++

Microsoft - Brand, Quality, Office, New Hardware++

Others - Price?